[Phys-seminars] 2018-04-11 Astrophysics and Cosmology Seminar

zitrin zitrin at bgu.ac.il
Mon Apr 9 08:42:10 IDT 2018

Astrophysics and Cosmology Seminar

 DATE: 11-04-18

 TIME: 11:15

 PLACE: Physics building (#54) room 207

A study of galaxy clusters through gravitational lensing: mass density profile and cluster abundance

Dr. Nathalia Cibirka, BGU

Dark matter halos associated with galaxy clusters are the biggest structures to have reached dynamical equilibrium, playing a central role both in providing cosmological information as well as astrophysical properties. Numerical simulations based on the ΛCDM scenario exhibit a universal density profile for dark matter halos. This profile can be described by two parameters, where one of these measures the concentration of the halo, and the other is the mass. Because of the definition of the profile in terms of these quantities, we end up with a relation between mass and concentration. Such correlation is explained as a consequence of the time when the halo was assembled: assuming that the central region keeps the mean density of the universe when the halo was formed, the more massive halos, which were assembled in later stages assuming an hierarchical scenario, should present a lower concentration. Measurements of this relation therefore provide an opportunity to test structu
 re formation. As cosmological probes, the number density of galaxy clusters as a function of mass and redshift is sensitive to the parameters affecting the growth and power spectrum of the linear density perturbations. Specifically, the cluster abundance is sensitive to the matter density Ωm and to the present amplitude of density fluctuations characterized by σ8. In this talk I will explore both astrophysical and cosmological aspects using the CODEX survey, a sample of galaxy clusters initially identified from X-ray luminosity data and further selected by the richness estimates, covering an area of 10,000 sqr degrees. I will also give a brief overview of my current work on cluster strong lensing using the RELICS sample. Such analysis intendeds to uncover sets of multiple images from lensed background galaxies and high-z candidates, as well as provide detailed lens models, necessary to derive intrinsic properties of magnified sources.

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